It is generally known that there is a variety of ways in which to ophthalmoscopically examine the eye, and that they all require at least some degree of patient fixation. Fixation includes the act of attracting and keeping the patient's gaze in a nominally fixed direction in order to keep the eye steady. To date, however, approaches to patient fixation devices have been largely limited to static, discrete points of light (e.g. images on a fixed screen or physical objects simply placed in the patient's field of view).
In U.S. Pat. No. 3,883,235, Lynn, et al disclose the use of a monitor to track the patient's gaze, and allow for the adjustment of an image on a screen to compensate for the patient's lack of fixation during a visual field examination. This solution, however, simply accommodates the problem of a patient's inherent fixation difficulties, rather than solving it.
In U.S. Pat. No. 4,536,065 Sheingorn discloses the use of a fixation device for the eye testing of children that uses several movable and light-emitting toys which are housed in display panel and remotely controlled by foot of an optician.
Marshall (U.S. Pat. No. 5,293,532) and Kirchhuebel (U.S. Pat. No. 4,685,784) disclose the use of a fixed array of light emitting diodes (LEDs) in order to fixate the patient's gaze. Marshall makes use of LEDs embedded in a patch which is worn over one eye while the other is being observed. While this allows the image of the LEDs to appear at infinity, and thereby relax the eye muscles, it is nevertheless awkward and patients may find it uncomfortable. Kirchhuebel positions the LEDs further away from the eye such that they are only simultaneously visible when the patient's head is in a precise location.
In U.S. Pat. No. 6,705,726, Tanassi discloses the use of a multipurpose ophthalmic diagnostic device containing a liquid crystal display (LCD) for patient fixation. This device provides for the projection of various types of patterns and stimuli via an optical system onto the retina.
Accordingly, it is desirable to provide a system and method for patient eye fixation that is inherently flexible, dynamic, compact, and uncomplicated. This is especially true when used to image tissue with Optical Coherence Tomography (OCT), or Scanning Laser Ophthalmoscopy (SLO) systems, or when used to apply burns to the retina with a therapeutic device such as a laser photocoagulator, especially a scanning laser photocoagulator.